Most electronic devices have a metal side frame or metal shell structure. For example, the side frame and/or back cover of the entire device may be made of metal except for its front screen so that the entire device has a very expressive appearance with a strong metallic feeling, and has a largely-increased structural strength. However, such a metal side frame or shell structure greatly reduce clearance of antenna, which brings many difficulties to antenna design.
Thus, it may be considered that the metal side frame may be cut off at an antenna-related position and the cut-off part may be filled up with non-metal material to reserve a given clearance for the antenna so that the antenna can radiate signals out.